ABSTRACT
The fusion protein, nucleophosmin-anaplastic lymphoma kinase (NPM-ALK), results from the chromosome translocation t(2;5)(p23;q25) and is present in 50-70 percent of anaplastic large-cell lymphomas (ALCLs). NPM-ALK is a constitutively activated kinase that transforms cells through stimulating several mitogenic signaling pathways. To examine if the NPM-ALK is a potential therapeutic target in ALCL, we used siRNA to specifically downregulate the expression of the NPM-ALK in ALCL cell lines. In this report, we demonstrated viability loss in t(2;5)-positive ALCL cell lines, SUDHL-1 and Karpas 299 cells, but not in lymphoma cell lines without the chromosome translocation, Jurkat and Granta 519 cells. Further study demonstrated that the downregulation of NPM-ALK resulted in decreased cell proliferation and increased cell apoptosis. When used in combination with chemotherapeutic agents, such as doxorubicin, the inhibition of the NPM-ALK augments the chemosensitivity of the tumor cells. These results revealed the importance of continuous expression of NPM-ALK in maintaining the growth of ALCL cells. Our data also suggested that the repression of the fusion gene might be a potential novel therapeutic strategy for NPM-ALK positive ALCLs.
Subject(s)
Lymphoma, Large B-Cell, Diffuse/drug therapy , Protein-Tyrosine Kinases/antagonists & inhibitors , RNA, Small Interfering/therapeutic use , Apoptosis/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Chromosomes, Human, Pair 2 , Chromosomes, Human, Pair 5 , Down-Regulation , Humans , Lymphoma, Large B-Cell, Diffuse/genetics , Lymphoma, Large B-Cell, Diffuse/pathology , Protein-Tyrosine Kinases/genetics , Signal Transduction , Translocation, GeneticABSTRACT
Chromosomal translocation t(2;5) and the resulting fusion protein nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) are detected in 50% to 70% of anaplastic large cell lymphoma (ALCL), which is a T/null cell non-Hodgkin's lymphoma showing anaplastic morphology with cell surface expression of CD30. Because aberrant CD30 expression was also observed in the T-cell lymphoma derived from lineage-specific NPM-ALK transgenic mice, we tested the hypothesis that there might be a functional relationship between the two neoplastic-related proteins: NPM-ALK and CD30. In this study, we used the RNA interference method to modulate NPM-ALK protein expression in ALCL-derived, t(2;5)-positive Karpas 299 cells. We observed decreased CD30 expression when NPM-ALK was repressed. Further analysis suggested that JunB functioned as the mediator of NPM-ALK-derived CD30 transcriptional regulation. The NPM-ALK-repressed cells, which had low CD30 expression, were characterized with lower cell proliferation compared with cells in the control group, suggesting that altered CD30 expression may correlate to NPM-ALK-mediated tumor cell growth inhibition. Combination of NPM-ALK repression and CD30 ligand leads to significantly increased tumor cell growth inhibition compared with one method alone, suggesting its potential application for ALCL-specific cancer treatment.
